The invention relates to a seal arrangement and method which provides a very low friction mechanism.
In pipe inspection techniques, for example, there is a need to insert long lengths of cable, hoses, umbilicals or the like into the pipe and arrange for these to be towed or otherwise transported through the pipeline. The term xe2x80x98cablexe2x80x99 hereinafter is intended to encompass all such elongate flexible members.
In the case of fluid carrying pipelines, such as natural gas pipelines, it is necessary to seal the cable at the entry point to prevent loss of fluid carried in the pipe, i.e. xe2x80x98livexe2x80x99 pipeline conditions.
In the past, poor sealing occurred due to debris on the cable. If a tighter seal was utilised, then the greater degree of friction occurred limiting the effectiveness of cable travel, which may be required to be several hundred meters in length through the pipeline.
The invention is concerned with overcoming such disadvantages to provide a running seal that is fluid tight.
According to the invention there is provided a seal arrangement for a cable including means for providing a first fluid at a first pressure to counter a second fluid at a second pressure in a duct receiving the cable to provide a low friction barrier seal as the cable moves or is utilised through the duct.
Further according to the invention there is provided a method of sealing a cable passing through an aperture in a duct the method comprising: applying and maintaining a first fluid pressure around the cable to counter a second fluid pressure present in the duct to provide a barrier seal.